MediumCVE-2026-55655

    Red Hat: Improper Restriction of Communication Channel to Intended Endpoints (CVE-2026-55655)

    Published Last modified Sources: BSI, Red Hat, Msrc Update Guide, CVE.org

    What is affected, what to do

    A flaw was found in OpenSSH. A local unprivileged attacker on a Linux client host can hijack client-side X11 forwarding connections.

    Update Red Hat Enterprise Linux 10 to version 0:9.9p1-25.el10_2, Red Hat Enterprise Linux 10.0 Extended Update Support to version 0:9.9p1-7.el10_0.5, Red Hat Enterprise Linux 8 to version 0:8.0p1-30.el8_10.

    Affected
    • Red Hat Enterprise Linux 10 lt *..0:9.9p1-25.el10_2
    • Red Hat Enterprise Linux 10.0 Extended Update Support lt *..0:9.9p1-7.el10_0.5
    • Red Hat Enterprise Linux 8 lt *..0:8.0p1-30.el8_10
    • Red Hat Enterprise Linux 9 lt *..0:9.9p1-9.el9_8
    • Red Hat Enterprise Linux 9.2 Update Services for SAP Solutions lt *..0:8.7p1-30.el9_2.13
    • Red Hat Enterprise Linux 9.4 Update Services for SAP Solutions lt *..0:8.7p1-38.el9_4.10
    • Red Hat Enterprise Linux 9.6 Extended Update Support lt *..0:8.7p1-45.el9_6.5
    • Red Hat Hardened Images lt *..10.3p1-6.hum1
    • Red Hat OpenShift AI 3.0 lt *..1791818590
    • Red Hat OpenShift AI 3.0 lt *..1791818589
    • Red Hat OpenShift AI 3.0 lt *..1791818505
    • Red Hat OpenShift AI 3.0 lt *..1791818496
    • Red Hat OpenShift AI 3.0 lt *..1791818502
    • Red Hat OpenShift AI 3.0 lt *..1793042072
    • Red Hat OpenShift AI 3.2 lt *..1791818602
    • Red Hat OpenShift AI 3.2 lt *..1791818598
    • Red Hat OpenShift AI 3.2 lt *..1791818512
    • Red Hat OpenShift AI 3.2 lt *..1791818587
    • Red Hat OpenShift AI 3.2 lt *..1791818778
    • Red Hat OpenShift AI 3.3 lt *..1791818782
    • Red Hat OpenShift AI 3.3 lt *..1791818627
    • Red Hat OpenShift AI 3.3 lt *..1791818790
    • Red Hat OpenShift AI 3.3 lt *..1791818874
    • Red Hat OpenShift AI 3.3 lt *..1791818792
    • Red Hat OpenShift AI 3.3 lt *..1791818662
    • Red Hat OpenShift AI 3.3 lt *..1791818877
    • Red Hat OpenShift AI 3.4 lt *..1791883722
    • Red Hat OpenShift AI 3.4 lt *..1791881612
    • Red Hat OpenShift AI 3.4 lt *..1791885618
    • Red Hat OpenShift AI 3.4 lt *..1791881487
    • Red Hat OpenShift AI 3.4 lt *..1791881732
    • Red Hat OpenShift AI 3.4 lt *..1791883315
    • Red Hat OpenShift AI 3.4 lt *..1791881486
    • Red Hat OpenShift AI 3.4 lt *..1791881769
    • Red Hat OpenShift AI 3.4 lt *..1791885505
    • Red Hat OpenShift AI 3.5 lt *..1791819252
    • Red Hat OpenShift AI 3.5 lt *..1791818749
    • Red Hat OpenShift AI 3.5 lt *..1791819206
    • Red Hat OpenShift AI 3.5 lt *..1791818979
    • Red Hat OpenShift AI 3.5 lt *..1791819123
    • Red Hat OpenShift AI 3.5 lt *..1791818901
    • Red Hat OpenShift AI 3.5 lt *..1791820333
    • Red Hat OpenShift AI 3.5 lt *..1791819495
    • Red Hat OpenShift AI 3.5 lt *..1791819104
    • Red Hat Update Infrastructure 5 lt *..1786435483
    • Red Hat Update Infrastructure 5 lt *..1786533529
    • Red Hat Update Infrastructure 5 lt *..1787135742
    • Red Hat Update Infrastructure 5 lt *..1787241260
    Fixed in
    • Red Hat Enterprise Linux 10 0:9.9p1-25.el10_2
    • Red Hat Enterprise Linux 10.0 Extended Update Support 0:9.9p1-7.el10_0.5
    • Red Hat Enterprise Linux 8 0:8.0p1-30.el8_10
    • Red Hat Enterprise Linux 9 0:9.9p1-9.el9_8
    • Red Hat Enterprise Linux 9.2 Update Services for SAP Solutions 0:8.7p1-30.el9_2.13
    • Red Hat Enterprise Linux 9.4 Update Services for SAP Solutions 0:8.7p1-38.el9_4.10
    • Red Hat Enterprise Linux 9.6 Extended Update Support 0:8.7p1-45.el9_6.5
    • Red Hat Hardened Images 10.3p1-6.hum1
    • Red Hat OpenShift AI 3.0 1791818590
    • Red Hat OpenShift AI 3.0 1791818589
    • Red Hat OpenShift AI 3.0 1791818505
    • Red Hat OpenShift AI 3.0 1791818496
    • Red Hat OpenShift AI 3.0 1791818502
    • Red Hat OpenShift AI 3.0 1793042072
    • Red Hat OpenShift AI 3.2 1791818602
    • Red Hat OpenShift AI 3.2 1791818598
    • Red Hat OpenShift AI 3.2 1791818512
    • Red Hat OpenShift AI 3.2 1791818587
    • Red Hat OpenShift AI 3.2 1791818778
    • Red Hat OpenShift AI 3.3 1791818782
    • Red Hat OpenShift AI 3.3 1791818627
    • Red Hat OpenShift AI 3.3 1791818790
    • Red Hat OpenShift AI 3.3 1791818874
    • Red Hat OpenShift AI 3.3 1791818792
    • Red Hat OpenShift AI 3.3 1791818662
    • Red Hat OpenShift AI 3.3 1791818877
    • Red Hat OpenShift AI 3.4 1791883722
    • Red Hat OpenShift AI 3.4 1791881612
    • Red Hat OpenShift AI 3.4 1791885618
    • Red Hat OpenShift AI 3.4 1791881487
    • Red Hat OpenShift AI 3.4 1791881732
    • Red Hat OpenShift AI 3.4 1791883315
    • Red Hat OpenShift AI 3.4 1791881486
    • Red Hat OpenShift AI 3.4 1791881769
    • Red Hat OpenShift AI 3.4 1791885505
    • Red Hat OpenShift AI 3.5 1791819252
    • Red Hat OpenShift AI 3.5 1791818749
    • Red Hat OpenShift AI 3.5 1791819206
    • Red Hat OpenShift AI 3.5 1791818979
    • Red Hat OpenShift AI 3.5 1791819123
    • Red Hat OpenShift AI 3.5 1791818901
    • Red Hat OpenShift AI 3.5 1791820333
    • Red Hat OpenShift AI 3.5 1791819495
    • Red Hat OpenShift AI 3.5 1791819104
    • Red Hat Update Infrastructure 5 1786435483
    • Red Hat Update Infrastructure 5 1786533529
    • Red Hat Update Infrastructure 5 1787135742
    • Red Hat Update Infrastructure 5 1787241260

    Not sure whether and how you are affected? Ask a question about this vulnerability

    Metrics

    6.1

    Priority

    XIEM Effective CVSS: highest available CVSS rating from NVD and vendor data.

    Source: NVD, CVSS v3

    5.0

    CVSS v3

    Severity Medium on the scale from 0 to 10.

    Source: BSI, Red Hat, Msrc Update Guide, CVE.org

    0.1 %

    EPSS score

    Low — model estimates < 1% exploitation likelihood.

    Source: FIRST EPSS, percentile 2.1

    Show all metrics
    Severity
    Medium
    Priority (0–325)

    The priority score is a consolidated metric that condenses several individual signals into a single, action-guiding ranking: technical severity (CVSS), exploitation likelihood (EPSS), known-exploited status (KEV) and the context of the affected asset. The aim is to answer the only truly important question in vulnerability management: what first?

    Read in glossary
    44.37 Methodology
    Exploit maturity

    An exploit is code or a technique that specifically uses a concrete vulnerability to force unintended behaviour — such as executing code or escalating privileges. It is the tool that turns a theoretical flaw into a practical attack.

    Read in glossary
    no public PoC known
    XIEM Effective CVSS

    XIEM® is the tiered managed-security operating model from NEOSEC and a registered trademark of NEOSEC GmbH. It extends classic SIEM — the central collection, normalisation and correlation of security-relevant events — with endpoint forensics, network visibility and deception technology, and consolidates them into three building tiers: Sentry, Orchestrate and Command.

    Read in glossary
    6.1 Methodology
    CVSS v3

    CVSS is the globally established, open standard for assessing the technical severity of a vulnerability on a scale from 0 to 10. It describes how easily a flaw can be exploited and what damage it can cause — but not how likely its actual exploitation is. CVSS and the complementary EPSS deliberately answer different questions.

    Read in glossary
    5.0
    EPSS score

    The EPSS score is the absolute model output for an individual vulnerability: the estimated probability of real-world exploitation within the next 30 days, expressed as a value between 0 and 1 (i.e. 0 % to 100 %). A score of 0.42 means „the model estimates a 42 % chance of real-world exploitation within 30 days“.

    Read in glossary
    0.1 %
    Low — model estimates < 1% exploitation likelihood.
    EPSS percentile

    The EPSS percentile is the relative position of a vulnerability within all EPSS-scored CVEs, expressed as a value between 0 and 1. A percentile of 0.90 means „this CVE has a higher EPSS score than 90 % of all other scored CVEs“. Unlike the EPSS score, it is not a probability — but a positioning within a ranking.

    Read in glossary
    2.1
    Low — this CVE sits in the lower 10% of all CVEs scored today.
    KEV status

    The KEV catalogue is a list maintained by the US authority CISA of vulnerabilities for which active exploitation in the wild has been confirmed. It answers not the question „how severe?“ but „is it already being attacked?“ — thereby sharply prioritising patching.

    Read in glossary
    —
    Published
    CISA assessment (SSVC)
    Exploitation: none known · not automatable · Technical impact: partial
    Source: CISA Vulnrichment, as of 23 June 2026
    CWE

    CWE is a catalogue of typical weakness types in software and hardware — such as flawed input validation, unsafe memory handling or poor authentication. Where a CVE names a concrete vulnerability in a concrete product, a CWE describes the underlying class of defect.

    Read in glossary
    CWE-923

    Detection rules

    No NEOSEC detection rule is available for this vulnerability yet.

    Classification under NIS2 and CRA

    Rule-based classification from exploitation status and severity. It does not replace a case-by-case assessment.

    NIS2

    NIS2 is EU Directive (EU) 2022/2555 to raise the level of cybersecurity across the Union. It substantially broadens obligations compared with the first NIS directive: more sectors, mandatory risk management, staged reporting duties and personal accountability of senior management.

    Read in glossary
    Handle the vulnerability in regular vulnerability handling under Art. 21(2)(e) NIS2.
    CRA

    The CRA is EU Regulation (EU) 2024/2847 setting horizontal cybersecurity requirements for „products with digital elements“ — from industrial controllers and software to connected consumer devices. For the first time manufacturers must ensure security across the entire product lifecycle, handle vulnerabilities and provide security updates.

    Read in glossary
    From 11.12.2027, Annex I Part II CRA requires manufacturers of affected products with digital elements to handle vulnerabilities without delay and provide security updates.
    ISO/IEC 27001

    ISO/IEC 27001 is the internationally leading standard for an information security management system (ISMS). It describes a risk-based, process-oriented framework to systematically plan, implement, review and improve information security.

    Read in glossary
    Control A.8.8, management of technical vulnerabilities: assess relevance to your systems, plan remediation and keep evidence.

    Description

    A flaw was found in OpenSSH. A local unprivileged attacker on a Linux client host can hijack client-side X11 forwarding connections. This is possible by pre-binding the preferred abstract X socket name when X11 forwarding is enabled and a local UNIX-domain X socket is used. A successful attack can compromise the confidentiality of forwarded X11 traffic, including sensitive window contents and input, and may allow some manipulation of the forwarded session.

    Source: BSI WID Portal, BSI CSAF, redhat_csaf, Microsoft Security Update Guide, cvelistv5, NVD (NIST), CVE.org (MITRE)

    Affected products

    The following versions are affected. Older releases of the same product line are also vulnerable unless stated otherwise.

    Affected products
    Affected versionsFixed in
    Red HatRed Hat Enterprise Linux 10
    • < 0:9.9p1-25.el10_2
    • 0:9.9p1-25.el10_2
    Red HatRed Hat Enterprise Linux 10.0 Extended Update Support
    • < 0:9.9p1-7.el10_0.5
    • 0:9.9p1-7.el10_0.5
    Red HatRed Hat Enterprise Linux 6
    • —
    • —
    Red HatRed Hat Enterprise Linux 7
    • —
    • —
    Red HatRed Hat Enterprise Linux 8
    • < 0:8.0p1-30.el8_10
    • 0:8.0p1-30.el8_10
    Red HatRed Hat Enterprise Linux 9
    • < 0:9.9p1-9.el9_8
    • 0:9.9p1-9.el9_8
    Red HatRed Hat Enterprise Linux 9.2 Update Services for SAP Solutions
    • < 0:8.7p1-30.el9_2.13
    • 0:8.7p1-30.el9_2.13
    Red HatRed Hat Enterprise Linux 9.4 Update Services for SAP Solutions
    • < 0:8.7p1-38.el9_4.10
    • 0:8.7p1-38.el9_4.10
    Red HatRed Hat Enterprise Linux 9.6 Extended Update Support
    • < 0:8.7p1-45.el9_6.5
    • 0:8.7p1-45.el9_6.5
    Red HatRed Hat Hardened Images
    • < 10.3p1-6.hum1
    • 10.3p1-6.hum1
    Red HatRed Hat OpenShift AI 3.0
    • < 1791818496
    • < 1791818502
    • < 1793042072
    • < 1791818589
    • < 1791818590
    • < 1791818505
    • 1791818496
    • 1791818502
    • 1793042072
    • 1791818589
    • 1791818590
    • 1791818505
    Red HatRed Hat OpenShift AI 3.2
    • < 1791818598
    • < 1791818587
    • < 1791818778
    • < 1791818512
    • < 1791818602
    • 1791818598
    • 1791818587
    • 1791818778
    • 1791818512
    • 1791818602
    Red HatRed Hat OpenShift AI 3.3
    • < 1791818877
    • < 1791818627
    • < 1791818874
    • < 1791818792
    • < 1791818790
    • < 1791818662
    • < 1791818782
    • 1791818877
    • 1791818627
    • 1791818874
    • 1791818792
    • 1791818790
    • 1791818662
    • 1791818782
    Red HatRed Hat OpenShift AI 3.4
    • < 1791883722
    • < 1791885618
    • < 1791881612
    • < 1791881487
    • < 1791885505
    • < 1791881769
    • < 1791881486
    • < 1791883315
    • < 1791881732
    • 1791883722
    • 1791885618
    • 1791881612
    • 1791881487
    • 1791885505
    • 1791881769
    • 1791881486
    • 1791883315
    • 1791881732
    Red HatRed Hat OpenShift AI 3.5
    • < 1791818749
    • < 1791818901
    • < 1791819123
    • < 1791820333
    • < 1791819206
    • < 1791819104
    • < 1791819252
    • < 1791818979
    • < 1791819495
    • 1791818749
    • 1791818901
    • 1791819123
    • 1791820333
    • 1791819206
    • 1791819104
    • 1791819252
    • 1791818979
    • 1791819495
    Red HatRed Hat OpenShift Container Platform 4
    • —
    • —
    Red HatRed Hat OpenShift Container Platform 5
    • —
    • —

    Vendors and products

    Affected operating systems

    Affected operating systems
    Linuxredhatenterprise_linux10.0
    Linuxredhatenterprise_linux6.0
    Linuxredhatenterprise_linux7.0
    Linuxredhatenterprise_linux8.0
    Linuxredhatenterprise_linux9.0

    Weakness classes (CWE)

    • CWE-923Improper Restriction of Communication Channel to Intended Endpoints

      Class

      The product establishes a communication channel to (or from) an endpoint for privileged or protected operations, but it does not properly ensure that it is communicating with the correct endpoint.

      Entry at MITRE CWE-923

    References & sources

    Changes to this CVE

    Who changed this CVE and when: NVD (analysis, affected products, CVSS), the CVE publisher (CNA) and additional providers such as CISA (ADP).

    1. Record modifiedRed Hat

      1 individual change: Affected versions (publisher)

      Show the original change
      Individual changes of this event as published by NVD
      TypeActionBeforeAfter
      Affected versions (publisher)added
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      Affected value modified. <a href="https://github.com/CVEProject/cvelistV5/blob/main/cves/2026/55xxx/CVE-2026-55655.json">CVE-2026-55655</a>

      Source identifier: secalert@redhat.com

    2. Record modifiedRed Hat

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      Referenceadded
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      https://access.redhat.com/errata/RHSA-2026:91232

      Source identifier: secalert@redhat.com

    3. Record modifiedRed Hat

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      Affected value modified. <a href="https://github.com/CVEProject/cvelistV5/blob/main/cves/2026/55xxx/CVE-2026-55655.json">CVE-2026-55655</a>
      Referenceadded
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      https://access.redhat.com/errata/RHSA-2026:89739

      Source identifier: secalert@redhat.com

    4. Record modifiedRed Hat

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      https://access.redhat.com/errata/RHSA-2026:82750
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      https://access.redhat.com/errata/RHSA-2026:82923

      Source identifier: secalert@redhat.com

    5. Record modifiedRed Hat

      Show 2 original changes
      Individual changes of this event as published by NVD
      TypeActionBeforeAfter
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      https://access.redhat.com/errata/RHSA-2026:82749

      Source identifier: secalert@redhat.com

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    1. Record modifiedRed Hat

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      https://access.redhat.com/errata/RHSA-2026:80513

      Source identifier: secalert@redhat.com

    2. Record modifiedRed Hat

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      https://access.redhat.com/errata/RHSA-2026:76993

      Source identifier: secalert@redhat.com

    3. Record modifiedRed Hat

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      https://access.redhat.com/errata/RHSA-2026:76748

      Source identifier: secalert@redhat.com

    4. Record modifiedRed Hat

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      Source identifier: secalert@redhat.com

    5. Record modifiedRed Hat

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      TypeActionBeforeAfter
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      Red Hat Enterprise Linux 10, Red Hat Enterprise Linux 8, Red Hat Enterprise Linux 8 (+8)
      Red Hat Enterprise Linux 10, Red Hat Enterprise Linux 8, Red Hat Enterprise Linux 8 (+8)

      Source identifier: secalert@redhat.com

    6. Record modifiedRed Hat

      Show 3 original changes
      Individual changes of this event as published by NVD
      TypeActionBeforeAfter
      Referenceadded
      —
      https://access.redhat.com/errata/RHSA-2026:47756
      Referenceadded
      —
      https://access.redhat.com/errata/RHSA-2026:47757
      Affected versions (publisher)changed
      Red Hat Enterprise Linux 8, Red Hat Enterprise Linux 8, Red Hat Hardened Images (+5)
      Red Hat Enterprise Linux 10, Red Hat Enterprise Linux 8, Red Hat Enterprise Linux 8 (+6)

      Source identifier: secalert@redhat.com

    7. Record modifiedRed Hat

      Show 2 original changes
      Individual changes of this event as published by NVD
      TypeActionBeforeAfter
      Referenceadded
      —
      https://access.redhat.com/errata/RHSA-2026:47755
      Affected versions (publisher)changed
      Red Hat Hardened Images, Red Hat Enterprise Linux 10, Red Hat Enterprise Linux 6 (+4)
      Red Hat Enterprise Linux 8, Red Hat Enterprise Linux 8, Red Hat Hardened Images (+5)

      Source identifier: secalert@redhat.com

    8. Initial analysis by NVDNVD

      Newly listed as affected:

      CVSS V3.1: AV:L/AC:L/PR:N/UI:R/S:U/C:H/I:L/A:N

      Show 4 original changes
      Individual changes of this event as published by NVD
      TypeActionBeforeAfter
      CVSSadded
      —
      AV:L/AC:L/PR:N/UI:R/S:U/C:H/I:L/A:N
      Product configurationadded
      —
      OR *cpe:2.3:o:redhat:enterprise_linux:7.0:*:*:*:*:*:*:* *cpe:2.3:o:redhat:enterprise_linux:6.0:*:*:*:*:*:*:* *cpe:2.3:a:openbsd:openssh:-:*:*:*:*:*:*:* *cpe:2.3:o:redhat:enterprise_linux:8.0:*:*:*:*:*:*:* *cpe:2.3:o:redhat:enterprise_linux:9.0:*:*:*:*:*:*:* *cpe:2.3:o:redhat:enterprise_linux:10.0:*:*:*:*:*:*:*
      Reference typeadded
      —
      Red Hat, Inc.: https://access.redhat.com/security/cve/CVE-2026-55655 Types: Vendor Advisory
      Reference typeadded
      —
      Red Hat, Inc.: https://bugzilla.redhat.com/show_bug.cgi?id=2462250 Types: Issue Tracking, Vendor Advisory

      Source identifier: nvd@nist.gov

    9. ReceivedRed Hat

      CVSS V3.1: AV:L/AC:H/PR:L/UI:R/S:U/C:H/I:L/A:N

      Weakness type: CWE-923

      Description added or changed

      Show 6 original changes
      Individual changes of this event as published by NVD
      TypeActionBeforeAfter
      Affected versions (publisher)added
      —
      Red Hat Enterprise Linux 10, Red Hat Enterprise Linux 6, Red Hat Enterprise Linux 7 (+4)
      Descriptionadded
      —
      A flaw was found in OpenSSH. A local unprivileged attacker on a Linux client host can hijack client-side X11 forwarding connections. This is possible by pre-binding the preferred abstract X socket name when X11 forwarding is enabled and a local UNIX-domain X socket is used. A successful attack can compromise the confidentiality of forwarded X11 traffic, including sensitive window contents and input, and may allow some manipulation of the forwarded session.
      CVSSadded
      —
      AV:L/AC:H/PR:L/UI:R/S:U/C:H/I:L/A:N
      Weakness type (CWE)added
      —
      CWE-923
      Referenceadded
      —
      https://access.redhat.com/security/cve/CVE-2026-55655
      Referenceadded
      —
      https://bugzilla.redhat.com/show_bug.cgi?id=2462250

      Source identifier: secalert@redhat.com

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